Proposals (Phase 1)

HSC queue mode proposals are submitted as Subaru Open Use programs, and all the basic policies of the Open Use apply to QM. For more information, see:

https://www.naoj.org/Observing/Visit/policy.html

A separate template is provided for the QM programs. The difference is that in QM the time is allocated in units of hours, where 1 h = 0.1 nights. PIs must first choose between classical and queue (recommended) modes, and estimate the number of required hours (on-source). The approximate dates of HSC runs, including the QM, will be communicated together in the call for proposals (CfP). Gemini and Keck Telescope partners can apply through time exchange for QM observations. Time-critical programs are acceptable, and cadence observations are allowed only in the form of monitoring proposals (see Monitoring proposals). Some additional limitations may apply (see CfP for details). For the latest policy changes, please check the QM website, which is typically updated more often that the present document.

Proposal preparation

Additional targets

An important policy of the HSC operation, including QM, is the “no additional targets” rule, which means that all targets must be defined at the Phase 1 stage, and (with the exception of very special cases) no new targets will be allowed to include in the program during the OB preparation stage and observations stage.

Some science programs may benefit from proposing more targets than may be possible to observe in the requested time, and defining the final sample after the acceptance and time allocation. During Phase 2 it is also possible to submit list of targets, where the total on-source time exceeds the allocation. Targets within one program can also be prioritized.

Some other restrictions apply to the selection of targets for HSC QM. See the “Clearly Prohibited Cases” in:

https://www.naoj.org/Observing/Visit/policy.html

Observing Constraints

During the observing night, the selection of targets to be observed depends on current conditions, especially seeing, sky transparency, sky brightness (Moon phase) and distance to the Moon. Night observing schedules will be adjusted accordingly, if weather changes. For each individual target they are set in the Phase 2, but the strictest ones must be well defined already in the Proposal.

In their proposals, the PIs should explicitly give the following information:

Seeing
the maximum value of seeing, at which observation may be performed, in arcsec.
Sky transparency
the sky clearness and magnitude drop due to clouds, defined as a number between 0 (totally cloudy) and 1 (clear).
Moon phase/sky brightness
the acceptable brightness of the sky, coming from the illumination and elevation of the Moon - “dark” or “gray”. “Dark” is 0-3 days from the new moon or while the moon is set. “Gray” time is defined when the moon is over the horizon between 4-11 days. HSC runs are not allocated during bright time.
Moon distance
the minimum separation from the Moon, at which the target can be observed, in degrees. Only distances larger than 30 deg are allowed (to avoid significant contamination with stray light). For “dark” time, 30 deg is set by default, and cannot be changed by the PI. For “gray” time, it is the PI who sets the constraint.
Time constraints
window of time when the PI wants the observations to be performed. There are no particular limits for its length, and multiple windows are allowed. It is allowed to put several targets per window, or define several windows for one object. Note that the chance for the OBs to be observed becomes higher by specifying the time windows as relaxed as possible.

NB Observation constraints in the proposal (item 13 in the application form) should be the strictest value for each constraint : seeing (upper limit), transparency (T; lower limit), Moon phase (brightest allowable phase), and Moon distance (lower limit). For example, if one target requires seeing \(\lesssim 0.8"\) while the others can be observed with seeing \(\sim1.6"\), the PI needs to set the seeing constraint as \(\lesssim 0.8"\) in item 13 of the ProMS.

Note that if an OB of a highly-ranked program is intended for restrictive conditions (for example seeing \(\le 0.8''\)) that are not currently met (\(\sim1.0''\)), this OB will not be executed at such moment, and a lower-ranked one that allows for given conditions (\(\le 1.0''\)) will be chosen. Relaxing the constraints increases the probability of performing observations. Defining different constraints for different targets is allowed.

In order to help choose the optimum observing constraints for a project, which will increase the probability of execution and still allow to accomplish the science goal, the PIs should familiarize themselves with the Statistical Information for Observing Condition Constraints in:

https://www.naoj.org/Observing/queue/phase1/

Time-critical observations may be proposed. If the PI requires the targets to be observed at a specific time, please provide sufficient information, such as: date(s), time, and duration of the time windows. Use the Box 13 of the Application Form, or add comments in the target list (see Queue proposal template and submission via ProMS). Note that the chance for the OBs to be executed may increase by specifying the time windows as relaxed as possible. If during the proposed time window the environmental conditions (seeing, transparency, etc.) are not met, the observations will not be carried out.

Filters

The filter exchange unit of the HSC can hold up to 6 filters in one observing run. Their list for given semester and given run, including QM runs, is published together with the CfP. See the following links for the availability and characteristics of HSC filters:

https://www.naoj.org/Instruments/HSC/sensitivity.html

QM proposals requesting filters which are not scheduled for the given semester will be rejected. Please note that the r and i-band filters have been replaced with new ones – r2 and i2. Please use only the new names in the proposal. The specifications of the old filters are still given, for comparison. They will still be stored, but will no longer be available, with the exception of special cases. Such cases should be properly justified. Please contact before submitting a proposal using the old r and i filters.

Overall, there are 5 broad band filters (BBF) and a number of narrow band filters (NBF). Note, however, that NBFs are user-owned filters, and to use them in your program you must first get the approval. For this reason the usage of NBFs is subject to slightly different policies, regarding calibrations for example (see further Sections).

Note also that to change the filter during the night, the telescope has to be pointed to the zenith and the dome has to be closed. The whole filter changing procedure takes approximately 0.5 h, and in general we try to minimize the number of such operations. If your program requires observations of the same field in several filters, very likely they will not be performed in the same night.

Proposals requesting to use narrow-band filters with their central wavelength shorter than 400 nm must only be submitted to classical mode, and will not be accepted in queue mode. Currently, this applies to filters NB387, NB391, and NB395.

Dithering

**HSC dither patterns: a) the pre-defined 5-point pattern; b) an example of a circular pattern with N = 5 (TDITH = θ degrees, RDITH = *r_D* arcsec and NDITH = N).**

The chips of the HSC are separated by small gaps (up to 53 arcsec) and some parts have defects (see deatils here), so to avoid having a target fall in such gap or bad chip, and to ensure complete coverage of the whole field of view, dithering is used. Dithering procedures for HSC are similar to the ones available for Suprime-Cam (see Commands for main exposures for S-Cam). In particular, there is a pre-defined 5-point dither pattern, a customized N-position circular pattern, and no-dither option is allowed as well. The pre-defined 5-point and 5-position circular patterns are recommended. Only one single exposure is taken on one position, which means that the recommended patterns will result in 5 exposures for a given field.

In the pre-defined 5-point dither, the user defines the steps dRA and dDEC, in arcsec, and the telescope points according to the scheme depicted above [HSC dither pattern (a)]. In the circular case, the user defines the radius \(r_{D}\) in arcsec, initial angle \(\theta\) in degrees, and number of steps \(N\) (5 recommended). Consecutive exposures are taken at positions that lay on a common circle of radius \(r_{D}\), every \(360^\circ / N\) from each other, as in the figure above [HSC dither pattern (b)]. Note that this is not done by rotation of the instrument, but by moving the telescope; the position angle of the instrument remains constant. The suggested values are \(120''\) for dRA, dDEC, and \(r_{D}\); and \(15^\circ\) and \(10^{\circ}\) for \(\theta\) in the case of \(N\neq 5\) and \(N=5\), respectively.

If one sequence, either pre-defined 5-point or circular, takes a lot of time, it may be split into two or more, using the parameters SKIP and STOP. For example, \(\mathit{STOP}=3\) means that the telescope will observe only in the first three positions, \(\mathit{SKIP}=3\) means that the telescope will start from the 4-th position, skipping the first three. \(\mathit{SKIP}=1\) and \(\mathit{STOP}=2\) will make the telescope move only to the second position. \(\mathit{STOP}\) must always be larger than \(\mathit{SKIP}\).

Without dithering, it may be necessary to introduce an offset to the target position, in order to avoid placing it in a gap between the CCDs.

See the following link for details:

https://www.naoj.org/Instruments/HSC/ope.html

ETC and overheads

<b><i>SNR</i> vs. exposure time and target AB magnitude for
the HSC-<i>z</i> filter</b> — *SNR* vs. exposure time and target AB magnitude for the HSC-z filter.

<b><i>SNR</i> variations due to the phase
and distance to the Moon.</b> — *SNR* variations due to the phase and distance to the Moon.

The total requested time given in the proposal must include overheads (detectors readout, slewing time, calibrations, etc.), as the number of hours per night has been redefined to match the classical mode (1 hour = 0.1 nights).

There is an exposure time calculator (ETC) dedicated to HSC, and the QM PIs are encouraged to use it:

https://hscq.naoj.hawaii.edu/cgi-bin/HSC_ETC/hsc_etc.cgi.

This is a python-based script that is called through a simple cgi web interface. It assumes that the total noise comes from: photon noise, sky brightness level (as a function of Moon phase and distance), and detector properties such as dark current and read-out noise. It also calculates the sky level, on the basis of Moon phase, Moon distance, and the selected filter. The usage of this script is explained as follows.

First in “Brightness” choose the appropriate filter and magnitude (in the AB system) of the source. In case of extended sources, use surface brightness in arcsec\(^2\). Then select between point and extended source. In the first case, give the desired value of seeing (in arcsec), in the latter, give the solid angle (size, in arcsec\(^2\)). Next, define the observing conditions, namely the Transparency (0–1), Moon (days to/from the new Moon, and Moon distance), and (for point sources) the diameter of the aperture that will be used for photometry. Finally, set the maximum sky brightness level (counts, in ADU) to be used to determine the number of frames.

To calculate the exposure time required to reach a certain , give the desired S/N ratio and click “Calculate exposure time”. The number of frames is ignored in this option. As results, the ETC will compute the total exposure time, limiting magnitude, saturation magnitude (assuming significant non-linearity at 45000 ADU), and the suggested number of frames. If the number of frames is more than 1, the exposure time, limiting magnitude and per frame are also given. The output also contains the sky level (in ADU/frame). At the end, the total time necessary to execute the observations (with overheads) is computed.

To calculate the expected after a certain exposure time, specify the time in seconds. Choose if it refers to the total time, or to one frame, and in the latter case, set the number of frames. After clicking “Calculate S/N ratio” the procedure will give the reached after the total exposure time (“Exp Time”\(\times\)number of frames, if such option is chosen), as well as in each frame. Total and per frame limiting magnitudes, as well as the saturation magnitude and sky level in ADU, will be computed. If the number of frames is specified, and the sky level exceeds the maximum value given earlier, we suggest to shorten the “Exp Time” and increase the number of frames. If “in total” option is chosen, the ETC splits the observation into multiple frames automatically. As before, the total time necessary to execute the observations (with overheads) is also computed.

Currently, the ETC does not include dithering patterns. Set the number of frames accordingly to your desired dither. To simulate several exposures per dither position (coadds), multiply the number of frames accordingly. For example: set 5 frames if you use the pre-defined 5-point dither, but if the resulting sky level is higher than the maximum sky count given, set frames to 10, 15, 20, etc.

In the future, a stand-alone python code will be available for off-line use.

In addition to the ETC, there is also an "HSC overhead and required time calculator", which is to be used to calculate the total requested time for the observing plan:

https://www.naoj.org/cgi-bin/ohc.cgi

The usage of this calculator is as follows. PIs must include at the time of the proposal submission 40 sec per exposure as overheads for readout and dithering, as well as 1.2 hours per night to their total request for the other overheads. This latter, operation-related overhead, is shared by all programs, with the amount proportional to the effective on-source exposure time per night. Note that the length of a night is assumed to be 10 hours; therefore, the effective length of the night used for queue proposals is (10-1.2) = 8.8 hours. Here, the 1.2 hours per night for the operation-related overheads (calibrations, focusing, filter exchanges and telescope slew) is an average value calculated based on former observing records. For more details, consult

https://www.naoj.org/Instruments/HSC/hsc_queue_overhead.html

Calibrations

QM users will not be charged time (i.e. do not have to include it in Phase 1 or 2) for standard calibrations, which are:

Bias
10 frames per each run.
Dark frame
5 frames of 300 sec per run.
Dome flat
for each run, dome flats for all 5 or 6 filters will be taken, but only one per night.

NB: Standard stars

Since the latest HSC pipeline uses the Pan-STARRS catalogue which covers entire skies observable from Hawaii, standard star calibrations are not necessary (some observers may recall that it used to be customary to take one or two short, i.e., 30-sec, exposures in SDSS fields for flux calibration purposes). If you do, however, require some specific standard stars to be observed, please prepare separate OBs. Please note that these additional OBs will be charged (i.e., the allocated time will accordingly be consumed). For OBs requiring narrow- and intermediate-band filters, a nearest spectrophotometric standard star to science fields will be observed immediately before or after science targets and it is free of charge.

Queue proposal template and submission via ProMS

Submission of Subaru proposals is done on-line through the ProMS 2.0 system:

https://proms.naoj.hawaii.edu/proms2/login.php

This is a web form that has an embedded template, which is used to create a final pdf document that is sent to the TAC and referees. From this page one can also obtain current semester templates, which can be used to prepare proposals off-line. After login to the ProMS system, one can choose to create a new proposal from scratch, or to load a tex file. One can log in using either the STARS or ProMS ID/password.

**ProMS menu since S17A: *Left*: The “Noral+Intensive program” part, from which the normal HSC QM proposal can be selected. *Right*: QM Filler template, with major differences marked.**

Normal Program

A separate tex template for Normal Queue Mode will be available. Inside the ProMS system, the normal QM proposals can be selected from the field “Normal+Intensive program” (Left figure above). The major difference with respect to the classical mode is box 12. “Observing Run” (Right figure above). Here the PI should give the number of hours (not nights) and specify the observing constraints (see Observing constraints section). The instrument is fixed to “HSC” and no 2nd choice can be given. The total and minimum requested time is also given in hours, not nights. There is no need to have a backup program or provide scheduling requirements other than those necessary to define time constraints.

If time-critical observations are requested, one should write "Time critical" in Comments in Box 12, and provide sufficient information on the time constraint (i.e., acceptable time windows) in Box 13 of the Application Form. If different constraints apply to different targets/fields, one should define the constraints in the list of targets, by adding comments in the "Magnitude" field. Multiple time windows are allowable. The time constraints of the windows should be clearly described, preferably in UT time. The time windows are limited by the number of queue nights in the semester.

Other fields and boxes should be filled similarly to a classical mode program:

https://www.naoj.org/Proposals/howto.html

Intensive Program

The same applies for Intensive proposals as for Normal programs, but the PI needs to uncomment \intensive in box 7 of the application form.

Filler

A separate LaTeX template for Filler Queue Mode will be available. Inside the ProMS system, the filler QM proposals can be selected from the field “Service program” (Left figure above). The template itself is however quite different (Right figure above), and no scientific justification is required for HSC QM fillers. Boxes 1 (Title), 2 (Investigators), 5 (Targets) and 6 (Archive) are the same as for other kinds of applications. The Abstract in box 3 should briefly describe the scientific aim and methods. In box 4 “Observing Run” one should select “HSC’ as the instrument, specify the number of requested hours (\(\le 35\)), and set the transparency, seeing, and filters. Time-critical programs may be acceptable as Fillers, but the chance of OB execution might be small unless the PI sets very relaxed time constraints. Since ProMS cannot accept proposals with identical title, the PIs submitting filler proposals which have similar scientific objectives to their Normal or Intensive proposals have to use a different title.

Evaluation and ranking

Time allocation committee (TAC)

HSC QM proposals will be reviewed by external referees, who will evaluate their scientific content, and by Subaru support astronomers (SAs), who will check the technical feasibility. The time allocation committee (TAC) will then select and rank the proposals based mainly on the referee score. Filler proposals will not be sent to referees, and only the TAC will review them and decide about their acceptance.

Grade

Based on the scientific evaluation, the TAC will assign a Grade to each of the submitted proposals.

Grade A
will be given to QM proposals having a high score. The observatory will put the highest effort to complete these programs. However, even if they are incomplete, they will not be carried over to the next semester. Please reapply if missing data are crucial to the completion of your project.
Grade B
will be given to the rest of accepted HSC QM proposals.
Grade C
will be given to the non-accepted proposals, which, however, will get the permission from the TAC to be observed. In this way the TAC will ensure that there are more programs than necessary to fill the time reserved for QM, which gives more flexibility and backup options during observations. Grade C observations will be performed in good or reasonable weather, when there are no A or B targets.
Grade F
will be given to the Filler proposals, i.e. those intended for bad weather (transparency \(\le 0.4\) and/or seeing \(\ge 1.6''\)). Filler programs might also be executed during classical nights, if the current classical program has no adequate backup.

When the constraints of a Grade A, B, or C proposal are found to be too severe, they become a subject of “relaxation”, in order to increase the probability of their execution. This may be requested by the TAC, or by SAs during Phase 2, or even during the observing run (see Changes in OBs).

Acceptance letters (AL)

After the proposal evaluation, each PI will receive an acceptance letter (AL), not later than two weeks after the TAC meeting. The AL will include such information as: acceptance judgment, referee score, Grade, and comments from referees and SAs. For Grade B and C proposals, in the AL the TAC may also ask to relax the observing constraints. Moreover, the ALs will include the request for preparation of OBs (Phase 2; see next chapter), together with all necessary deadlines and web addresses, as well as the values of the total allocated time and observing constraints (used for OB validity check, see next Chapter).

Grade C program PIs will be asked whether they still wish to participate in the queue programs, given the fact that the completion rate of Grade C programs is very low, typically less than 10%. For Grade F, the TAC will notify whether the program was allowed for observations or not. Once the OBs for Grade C and F are submitted (Phase 2), there will be no further iteration process involving the PI, although the QWG may make minor changes.

Note that the proposal Grade may later be published, however the referee score and all comments will only be known to the PI.